Transcript Document
Contact lenses were
thought of as early as
1508 when Leonardo da
Vinci sketched and
described several forms of
them.
Contact lenses are a
changing area of
optometry with new lenses
being constantly
developed
Refractive errors are
corrected by contact
lenses, which are placed
directly on the cornea
pupil
cornea
iris
sclera
Lid
margin
conjunctiva
Normal focus
Short sightedness
(Myopia)
• Distance vision blurry, near usually OK.
Short-sighted
focus
Short-sighted
correction
Long-sightedness
(Hyperopia)
• Difficulty seeing clearly and comfortably
up close.
Long-sighted
focus
Long-sighted
correction
Astigmatism
• Irregular curvature of the eye (shaped
more like a football than a basketball)
• Light in different planes focuses at
different points
A
90
B
180
There are many types of
contact lenses
RGP lenses
Soft lenses
Disposable or non-disposable
Coloured or clear
Spherical or toric
Extended wear
Multifocal
RGP lenses (rigid gas
permeable)
Smaller than size of cornea
May be less comfortable than soft
lenses initially
Very effective in correcting astigmatism
RGP contact lens
Soft lenses
Most commonly used (90%)
Made from hydrogel plastic material
containing water
Are 1-2mm larger than cornea
Easy to adapt to
Soft contact lens
Spherical lenses
Correct short or long-sightedness
Cheapest, most comfortable lenses
Easy to get in disposable form
Toric lenses
Correct astigmatism
Lens is specially weighted to conform
to irregular cornea
More expensive than spherical
Some are available in disposable
Disposable lenses
Daily, two-weekly or monthly
replacement
Very simple cleaning (no cleaning
for daily)
Latest designs and materials
Very popular
Coloured lenses
Handling tint
Useful when inserting or removing
Enhancing tint
Makes light coloured eyes more vivid
Opaque tint
Can change brown eyes to blue
Extended wear lenses
New technology
Made from silicone material which
transmits oxygen well
Can wear for up to thirty days without
removing
Will not suit all people – your optometrist
will advise
Multifocal contact lenses
Can wear one reading lens, one distance
Can have dual focus lenses
New technology – slightly more expensive
Available as a disposable lens
Advantages of contact
lenses over glasses
Better field of view
No fogging up
No one has to know you have refractive
error
No frames – eg, useful for sport
Sometimes the vision is better
Hygiene is extremely
important with contact
lenses
Always wash your hands before
touching lenses
If lenses are not clean, bacteria can stick
to them
A tiny scratch on the eye can
get infected
If you have a sore, red eye
take your lenses out and
go to see your optometrist
ASAP
If properly looked after,
the chance of having an
infection with contact
lenses is extremely low
Consultations for contact
lenses
Contact lenses need to be fitted to each
individual eye
Several tests are required for:
measuring and trying the lenses
teaching insertion and removal
after care
Your optometrist can advise you about the
tests are required
Optometrists
Detect and diagnose
problems with eye health
Prescribe glasses or contact
lenses, if required
Diagnose and treat problems
with focusing
Optometrists
Are university educated and regularly
undertake continuing professional
education
No referral is required
To find an optometrist
Yellow pages
NZ Association of Optometrists
www.nzao.co.nz
0800 439 322